Refrigerant compositions

ABSTRACT

Refrigerant compositions are provided which include: (a) pentafluoroethane or trifluoromethoxydifluoromethane or hexafluorocyclopropane or mixtures thereof, in an amount from about 60 to about 70% by weight based on the weight of the composition; (b) 1,1,1,2- or 1,1,2,2-tetrafluoroethane or trifluoromethoxypentafluoroethane or 1,1,1,2,3,3 -heptafluoropropane or mixtures thereof, in an amount from about 26 to 36% by weight based on the weight of the composition; and (c) an ethylenically unsaturated or saturated hydrocarbon, optionally containing one or more oxygen atoms, having a boiling point from −12° C. to +10° C., or a mixture thereof, or a mixture of one or more of the hydrocarbons with one or more other hydrocarbons or ethers, said mixture having a bubble point from −12° C. to +10° C., in an amount from about 1% to 4% by weight based on the weight of the composition. Also provided is a process of refrigeration using the refrigerant compositions and a refrigeration apparatus containing the refrigerant compositions.

This application is a continuation-in-part of U.S. application Ser. No.10/053,569, filed Jan. 24, 2002, which, in turn, is a divisional of U.S.application Ser. No. 09/351,355, filed Jul. 12, 1999, now U.S. Pat. No.6,428,720. The present application claims priority based upon GreatBritain Applications No. GB 022789.9, filed Nov. 29, 2002 and GEB0228306.7, filed Dec. 4, 2002. The contents of all the aboveapplications are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to refrigerant compositions, particularlyfor use in refrigeration equipment and air conditioning systems.

BACKGROUND OF THE INVENTION

Refrigeration and air conditioning equipment frequently require largeamounts of cooling. Recently, R21(CHCIF₂) has been used for thispurpose. However, since R22 is an ozone depleter that will be phased outover the next decade, in accordance with the Montreal protocol, there isa need for an alternative refrigerant that has similar properties toR22, but is not an ozone depleter. Of particular concern is that thetemperature/vapour pressure relationship for such a refrigerant shouldbe sufficiently similar to R22 that it can be used in R22 equipmentwithout having to change the control systems which are usuallyprogrammed in the factory making the equipment.

This is of particular concern for systems that have sensitive controldevices, which rely on both the inlet pressure to the expansion valveand the outlet pressure. These control systems are based on R22properties. Therefore, if an R22 substitute does not have atemperature/vapour pressure behavior which is similar to R22, the systemwill not operate correctly.

By similar, it is meant that the vapour pressure of the substituteshould not differ from that of R22 by more than ±12% and preferably notmore than ±6% at any given mean evaporating temperature between −40° C.to +10° C. It is also important that any such refrigerant has a similarcapacity and efficiency as R22. Similar capacity means a capacity thatis no more than 20% lower than that of R22 and preferably not more than10% lower than k22 at mean evaporating temperatures between −35° C. to−28° C. Similar efficiency means not more than 10% lower than that ofR22 and preferably not more than 5% lower at mean evaporatingtemperatures between −35° to −28° C.

SUMMARY OF THE INVENTION

The present invention provides a refrigerant composition which comprisesa mixture of:

(a) pentafluorethane, trifluoromethoxydifluoromethane orhexafluorocyclopropane or a mixture of two or more thereof, in an amountof from about 60 to about 70% by weight based on the weight of thecomposition;

(b) 1,1,2- or 1,1,2,2-tetrafluorethane,trifluoromethoxypentafluoroethane, 1,1,1,2,3,3-heptafluoropropane or amixture of two or more thereof, in an amount of from about 26 to about36% by weight based on the weight of the composition; and

(c) an ethylenically unsaturated or saturated hydrocarbon, optionallycontaining one or more oxygen atoms, with a boiling point from −12° C.to +10° C., or a mixture thereof, or a mixture of one or more of saidhydrocarbons with one or more other hydrocarbons, said mixture having abubble point from −12° C. to +10° C., in an amount from about 1% toabout 4% by weight based on the weight of the composition. It hassurprisingly been found that these particular formulations haveproperties which enable them to be used as a replacement for R22.

The percentages quoted above refer, in particular, to the liquid phase.The corresponding ranges for the vapour phase are as follows:

(a) about 70 to 87%, (b) about 10-28%, and (c) about 0.9-4.1%, all byweight based on the weight of the composition. These percentagepreferably apply both in the liquid and vapor phases.

The present invention also provides a process for producingrefrigeration which comprises condensing a composition of the presentinvention and thereafter evaporating the composition in the vicinity ofa body to be cooled. The invention also provides a refrigerationapparatus containing, as refrigerant, a composition of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a graph showing vapor pressures of blends according to theinvention.

FIG. 2 is a graph depicting capacities for blends prepared according tothe invention.

FIG. 3 is a graph showing COP results for blends of the invention.

FIG. 4 is a graph showing COP results at a constant capacity forcompositions of the invention.

FIG. 5 is a graph showing the capacity of blends of the invention,

FIG. 6 is a graph comparing the COP of blends of the invention and R22.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Component (a) is present in an of amount from about 60 to about 70% byweight based on the weight of the composition. Preferably, theconcentration is about 62 to about 67%, especially above 64% and up to66%, by weight. Preferably, component (a) is R125 (pentafluorethane) ora mixture containing at least half, especially at least three quarters(by mass) of R125. Most preferably component (a) is R125 (alone).

Component (b) is present in the composition in an amount from about 26to about 36%, especially about 28 to about 32% by weight based on theweight of the composition. Component (b) is preferably a mixturecontaining at least half, especially at least three quarters (by mass)of R134a (1,1,1,2-tetrafluoroethane). Most preferably component (b) isR134a (alone).

The weight ratio of component (a) to component (b) is desirably at least1.5:1, preferably 1.5:1 to 3:1 and especially 1.8: 1 to 2.2:1.

Component (c) is a saturated or ethylenically unsaturated hydrocarbon,optionally containing one or more oxygen atoms, in particular one oxygenatom, with a boiling point from −12° C. to +10° C., especially −12° C.to −5° C. or a mixture thereof. Preferred hydrocarbons which can be usedcontain three to five carbon atoms. They can be acyclic or cyclic.Acyclic hydrocarbons or ethers which can be used include propane,n-butane, isobutane and ethylmethyl ether. Cyclic hydrocarbons which canbe used include methyl cyctopropane. Preferred hydrocarbons includen-butane and isobutane, with n-butane being especially preferred.Component (c) can also be a mixture of such a hydrocarbon with one ormore other hydrocarbons or ethers, said mixture having a bubble pointfrom −12° C. to +10° C., especially −12° C. to −5° C. Other hydrocarbonsor ethers which can be used in such mixtures includes pentane,isopentane, propene, dimethyl ether, cyclobutane, cyclopropane andoxetan.

The presence of at least one further component in the composition is notexcluded. Although the composition typically will comprise the threeessential components listed above, at least one further component canalso be present. Typical further components include fluorocarbons and,in particular, hydrofluorocarbons, such as those having a boiling pointat atmospheric pressure of at most −40° C., preferably at most −49° C.,especially those where the F/H ratio in the molecule is at least 1.Preferable fluorocarbons include R23 (trifluoromethane) and, mostpreferably, R32 (difluoromethane).

In general, the maximum concentration of these other ingredients doesnot exceed about 10%, preferably not exceeding 5% and most preferablynot exceed about 2% by weight, based on the sum of the weights ofcomponents (a), (b) and (c). The presence of hydrofluorocarbonsgenerally has a neutral effect on the desired properties of theformulation. Desirably one or more butanes, especially n-butane and/oriso-butane, represents at least about 70%, preferably at least about 80%and more preferably at least about 90% by weight of the total weight ofhydrocarbons in the composition. It will be appreciated that it ispreferable to avoid perhalocarbons so as to minimise any greenhouseeffect and to avoid hydrohalogenocarbons having halogens heavier thanfluorine. The total amount of such halocarbons should advantageously notexceed about 2% especially 1% and more preferably 0.5% by weight.

According to a preferred embodiment, the composition comprises, ascomponent (a), about 62 to 67% based on the weight of the composition ofpentafluoroethane; as component (b) about 3 to 35% by weight based onthe weight of the composition of 1,1,1,2-tetrafluoroethane; and ascomponent (c), butane or a mixture of hydrocarbons comprising butane.When component (c) is a mixture, the concentration of butane in themixture is preferably at least about 50% by weight, especially at least70% by weight, more preferably at least 80% by weight and even morepreferably at least 90% by weight, based on the weight of thecomposition. The other component of the mixture is preferably pentane.

It has been found that the compositions of the present invention arehighly compatible with the mineral oil lubricants conventionally usedwith CFC refrigerants. Accordingly, the compositions of the inventioncan be used with fully synthetic lubricants such as a polyol esters(POE), polyalkyleneglycols (PAG) and polyoxypropylene glycols or withfluorinated oil as disclosed in EP-A-399817 and also with mineral oiland alkyl benzene lubricants including napththenic oils, paraffin oilsand silicone oils and mixtures of such oils and lubricants with fullysynthetic lubricants and fluorinated oil.

The usually additives can be used including “extreme pressure” andantiwear additives, oxidation and thermal stability improvers, corrosioninhibitors, viscosity index improvers, pour point depressants,detergents, anti-foaming agents and viscosity adjusters. Examples ofsuitable additives are included in Table D in U.S. Pat. No. 4,755,316,the disclosure of which is incorporated herein in it entirety.

The invention will be illustrated by the following Examples which areintended to be merely exemplary and in no manner limiting.

EXAMPLES

The samples used for testing are detailed below:

-   Butane (3.5%) blend: R125/134a/600 (65.0/31/5/3.5)-   Isobutane (3.5%) blend: R125/134a/600a (64.9/31.7/3.4)    Equipment and Experimental

The samples, each approximately 600 g, used for the determination of thevapour pressures were prepared in aluminum disposable cans(Drukenbehalter—product 3469), which were then fully submerged in athermostatically controlled water bath. For each determination, the canwas charged with about 600 g. A maximum of two samples could beprocessed at any one time. The bath temperature was measured using acalibrated platinum resistance thermometer (152777/1B) connected to acalibrated Isotech TTI1 indicator. Pressure readings were taken usingthe two calibrated Druck pressure transducers, DR1 and DR2.

The temperature of the bath was set to the lowest temperature requiredand it was then left until it had cooled. When the temperature andpressure had remained constant for at least a quarter of an hour, theywere then recorded. Further temperature and pressure readings were takenin increments of 5° C. to a maximum of 50° C., each time ensuring thatthey were steady for at least a quarter of an hour before recordingthem.

The data obtained does not give the dew point and as such, does not givethe glide. An approximate evaluation of the glide can be obtained byusing the REFPROP 6 program. The relationship of the glide to the bubblepoint can be represented by a polynomial equation. This equation can beused to give an approximate glide for the experimentally determinedbubble points. This is effectively a normalisation of the calculatedglide to the experimentally determined data. The dew point pressures canthen be approximated by subtracting the temperature glide from thetemperature in the bubble point equation,

These equations are then used to obtain vapour/pressure tables. Theexperimental equation derived for the bubble points and the glideequation from REFPROP 6 are shown in Table 1.

Notes:

-   -   1. In this equation x=1/T, where T is the bubble point in        Kelvin: y=1n(p), where p is the saturated vapour pressure in        psia. To convert psia to MPa absolute pressure, multiply by        0.006895.    -   2. In this equation x=t, where t is liquid temperature (bubble        point) in degree C and y=glide in degree C at the bubble point        temperature.    -   3. The vapour pressures for R22 were obtained from the Ashrae        handbook by interpolation.        Determination of the Performance of the Refrigerants on the Low        Temperature (LT) Calorimeter        Equipment and General Operating Conditions

The performance of the refrigerants was determined on the lowtemperature (LT) calorimeter. The LT calorimeter is fitted with a Bitzersemi-hermetic condensing unit containing Shell SD oil. The hot vapourpasses out of the compressor, through an oil separator and into thecondenser. The discharge pressure at the exit of the compressor is keptconstant by means of a packed gland shut-off valve. This inevitably hasan effect on the condensing pressure/temperature—the system is actuallycondensing at a temperature below 40%C. The refrigerant then travelsalong the liquid line to the evaporator.

The evaporator is constructed from 15 mm Cu tubing coiled around theedges of a well-insulated 32-litre SS bath. The bath is filled with a50:50 glycol:water solution and heat is supplied by 3×1 kW heaterscontrolled by a PID controller. A stirrer with a large paddle ensuresthat the heat is evenly distributed. The evaporating pressure iscontrolled by an automatic expansion valve. The refrigerant vapourreturns to the compressor through a suction line heat exchanger.

Twelve temperature readings, five pressure readings, compressor powerand heat input are all recorded automatically using Dasylab. The testswere run at a condensing temperature of 40° C. and an evaporatorsuperheat of 8° C. (±0.5° C.). For R22 the temperature at the end of theevaporator was maintained at 8° C. above the temperature equivalent tothe evaporating pressure (bubble point). For the other refrigerants, thetemperature at the end of the evaporator was maintained at 8° C. abovethe temperature equivalent to the evaporating pressure (Dew point). Themean evaporator temperature for these refrigerants was calculated bytaking the temperature equivalent to the evaporator pressure from thebubble point table and adding to that half the glide at thattemperature,

When running the calorimeter, the evaporating and condensing pressuresare initially set to an approximate value along with the temperature ofthe bath. The calorimeter is then allowed time for the conditions tostabilise. During this period, coarse adjustments can be made.Conditions must also be monitored in order to ensure that sufficientheat is being put into the bath to avoid any liquid getting back to thecompressor. When the system is virtually steady, fine adjustments ofpressure and temperature are made until the calorimeter has stabilisedat the required evaporating pressure with a condensing pressureequivalent to 40° C. and an evaporator superheat of 8° C. (Note: thesuperheat is measured from the third evaporator outlet). The run is thencommenced and run for a period of one hour, during which time noadjustments are made to the system, except for possibly minor changes tothe condensing pressure to compensate for fluctuations in the ambienttemperature.

Specific Experimental Details for Each Refrigerant

R22: The calorimeter was charged with R22 (3.5 kg into the liquidreceiver). Ten data points were obtained between the evaporatingtemperatures of −38° C. and −22° C.

Butane (3.5%) blend: Approximately 3.55 kg were charged into the liquidreceiver and five data points were obtained between the mean evaporatingtemperatures of −38° C. and −22° C.

Isobutane (3.5%) blend: Approximately 3.48 kg of the blend were chargedinto the liquid receiver of the LT-calorimeter. Five data points betweenthe mean evaporating temperatures of −38° C. and −22° C. were obtained.

Results

The results obtained are summarised in Tables 2-4. Mean Ev. Temp=Meanevaporation temperature; Air on condenser=temperature of the air blowingover the condenser; Press=pressure.

The results obtained are shown graphically in Graphs 1 to 6. Graph 1shows the saturated vapour pressures for the blends investigated alongwith that for R22. The graph shows that the vapour pressures of theblends are only slightly higher than that for R22.

Graph 2 shows a comparison of the capacities with respect to R22 at amean evaporating temperature of −30° C., a typical temperature at whichthese blends would be expected to operate. At this temperature, thebutane blend is only 4% below the capacity of R22, and the capacity ofthe isobutane blend is 5.5% below that of R22.

The COP results obtained are shown in Graph 3. This graph shows that ata mean evaporating temperature of −30° C., the COP values of both thehydrocarbon blends are less than 1% below R22.

In Graph 4, the capacity is fixed to that of R22 at the evaporatingtemperature of −30° C. The COPs at this constant capacity for thedifferent refrigerants can now be compared. The graph shows that boththe butane blend (by 2.5%) and the isobutane blend (by 3.0%) are moreefficient than R22 for this given capacity.

The capacity of the hydrocarbon blends relative to R22 is shown in Graph5. The lines for the two blends are parallel to one another and thecapacities are similar with that of the isobutane blend being slightlylower.

Graph 6 shows the COP of the RX blends relative to R22. The COP of R22and that of the two blends is shown to be similar. The lines of thehydrocarbon blends cross over one another (and R22) at a meanevaporating temperature of −32° C. showing the increase in the relativeCOP of R22 and the decrease in the relative COP of the isobutane blend.As before, the differences are minimal. TABLE 1 Results of theexperimental SVP measurements and the glide from REFPROP6 SVP Glideequation Description Equation (see note 1) (see note 2) Butane (3.5%) y= −2347.45820x + y = −0.02618x + 3.51740 blend 12.96325 R² = 0.99790R125/134a/600 R² = 0.99999 (65.0/31.5/3.5) Isobutane (3.5%) y =−2356.045324x + y = −000001x³ − blend 12999729 0.000012x² − 0.028998x +R125/134a/600a R² = 0.999956 3.628716 (64.9/31.7/3.4) R22 (see note 3)Not applicable

TABLE 2 R22 CONDENSING AT 40° IN LT-CALORIMETER Mean Discharge Evap EvapEv. Discharge Air On absolute Condensing Evaporator Temp Temp CapacityEvap. Temp Temp Condenser Press Temp Inlet Press BUBBLE DEW CompressorHeat Input Superheat ° C. ° C. ° C. Mpa ° C. MPa ° C. ° C. Power kwh kwhC.O.P. ° C. −37.6 149.9 20.8 1.439 40.1 0.016 −37.6 −37.6 1.161 0.6140.53 8.3 −35.9 154.5 22.3 1.425 39.8 0.025 −35.9 −35.9 1.208 0.846 0.708.5 −34.0 156.1 22.2 1.433 40.0 0.036 −34.0 −34.0 1.283 1.031 0.80 8.3−31.6 156.3 22.9 1.438 40.1 0.051 −31.6 −31.6 1.375 1.282 0.93 8.3 −29.5455.7 23.4 1.450 40.4 0.065 −29.5 −29.5 1.388 1.412 1.02 7.8 −28.8 152.822.0 1.447 40.4 0.071 −28.8 −28.8 1.418 1.508 1.06 8.1 −28.1 154.7 23.91.430 39.9 0.076 −28.1 −28.1 1.457 1.586 1.09 8.4 −25.4 152.7 22.7 1.44940.4 0.096 −25.4 −25.4 1.593 1.992 1.25 8.0 −24.0 152.8 23.8 1.446 40.30.108 −24.0 −24.0 1.646 2.167 1.32 8.6 22.1 149.6 23.8 1.450 40.4 0.124−22.1 −22.1 1.688 2.387 1.41 8.4

TABLE 3 BUTANE (3.5%) CONDENSING AT 40° C. IN LT- CALORIMETER MeanEvaporator Evap Evap Capacity Ev. Discharge Air On Discharge CondensingInlet Temp Temp Heat Evap. Total Temp Temp Condenser absolute Tempabsolute BUBBLE DEW Compressor Input Superheat Superheat ° C. ° C. ° C.Press Mpa ° C. press MPa ° C. ° C. Power kwh kwh C.O.P ° C. ° C. −37.4114.1 20.8 1.528 39.9 0.025 −39.7 −35.1 1.094 0.629 0.58 7.7 47.0 −34.2115.8 21.6 1.529 39.9 0.044 −36.4 −31.9 1.237 0.976 0.79 7.9 43.5 −30.4112.1 21.1 1.539 40.2 0.068 −32.6 −28.3 1.336 1.317 0.99 7.8 39.7 −25.9108.9 21.4 1.540 40.2 0.102 −28.0 −23.8 1.459 1.729 1.18 8.0 36.7 −22.5106.8 22.6 1.543 40.3 0.132 −24.6 −20.4 1.592 2.161 1.36 8.3 35.5

TABLE 4 ISOBUTANE BLEND (3.5%) CONDENSING AT 40° C. IN LT-CALORIMETERMean Evaporator Evap Evap Capacity Ev. Discharge Air On DischargeCondensing Inlet Temp Temp Heat Evap. Total Temp Temp Condenser absoluteTemp absolute BUBBLE DEW Compressor Input Superheat Superheat ° C. ° C.° C. Press Mpa ° C. press MPa ° C. ° C. Power kwh kwh C.O.P ° C. ° C.−37.7 114.6 23.1 1.544 40.0 0.023 −40.1 −35.3 1.033 0.596 0.58 8.0 49.0−34.3 116.2 23.2 1.544 39.9 0.043 −36.6 −31.9 1.194 0.950 0.80 8.3 44.8−29.8 113.1 22.2 1.544 40.0 0.072 −32.1 −27.5 1.353 1.361 1.01 8.5 40.1−26.2 109.7 22.4 1.538 39.8 0.100 −28.4 −23.9 1.440 1.682 1.17 8.6 37.7−21.5 106.4 24.2 1.562 40.4 0.140 −23.6 −19.3 1.622 2.252 1.39 8.2 35.4

While the invention has been described with preferred embodiments, it isto be understood that variations and modifications may be resorted to aswill be apparent to those skilled in the art. Such variations andmodifications are to be considered within the purview and the scope ofthe claims appended hereto.

1-23. (canceled)
 24. A nonflammable composition consisting of: (a)pentafluoroethane in an amount from 62-67% by weight based on the weightof the composition; (b) 1,1,1,2-tetrafluoroethane in an amount from 26to 36% by weight based on the weight of the composition; (c) isobutanein an amount of from 1-4% by weight based on the weight of thecomposition; and (d) at least one lubricant.
 25. A nonflammablecomposition consisting of: (a) pentafluoroethane in an amount of from62% to 67% by weight based on the weight of the composition; (b)1,1,1,2-tetrafluoroethane in an amount of from 26% to 36% by weightbased on the weight of the composition; (c) isobutane in an amount offrom 3-4% by weight based on the weight of the composition; (d) at leastone lubricant; and (e) at least one additive.
 26. A nonflammablecomposition consisting of: (a) pentafluoroethane in an amount from 62%to 67% by weight based on the weight of the composition; (b)1,1,1,2-tetrafluoroethane in an amount of from 26% to 36% by weightbased on the weight of the composition; (c) isobutane in an amount offrom 3-4% by weight based on the weight of the composition; and (d) atleast one additive.
 27. The composition according to claim 24, 25 or 26in which component (c) is isobutene present in an amount of about 3.5%by weight based on the weight of the composition.
 28. The compositionaccording to claim 24, 25 or 26 in which component (b) is present in anamount about 28% to about 32% by weight based on the weight of thecomposition.